travis CI: remove hhvm-nightly (no longer supported on precise)
travis CI: remove hhvm-nightly (no longer supported on precise)

webdevid/scssphp,webdevid/scssphp,kkkyyy03/scssphp,webdevid/scssphp,g105b/scssphp,dleffler/scssphp,leafo/scssphp,leafo/scssphp,leafo/scssphp,dleffler/scssphp,g105b/scssphp,dleffler/scssphp,g105b/scssphp